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JSX: Taming the Amber Channel

Discussion in 'Amps and Cabs' started by DavidE, Jul 31, 2005.

  1. DavidE

    DavidE Member

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    I picked up a JSX head for my cover band hoping that the three channel versatility would negate the need for pedals and give me three killer sounds.

    I'm getting used to no reverb.

    I like the clean channel. It works great with pedals. No real complaints there.

    The amber channel sounds killer, but even at very low gain settings, it's very gainy and I have to use a TS9 or FDII on the clean channel for lower gain stuff. While this will work fine, I'm wondering if there's a way (maybe a preamp tube swap?) to lower the gain levels on the amber channel? I'd like the channel to start as a mild overdrive.

    Another local guy took out a pair of power tubes and said the amp really took off at club volumes with that change. I'll try that next weekend.

    The red channel? Very cool. No complaints. I love the way the active eq and fat switch make even this channel very full.

    It doesn't sound as great as my Naylor Electroverb 38, but it will do very nicely on the cover circuit.
     
  2. baron55

    baron55 Member

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    What kind of tubes are you running. Almost any of the New Sensor brand tubes Sovtek, Electro Harmonix, and the new mullard and tung sol imposters. All have one thing in common, grainy harshness.

    Tubes that sound good in the JSX are the JJECC803's, the ECC83's are good but loose high end sparkle. Also I am running SED EL34's and the Ruby EL34STB sound great to.
    Also setting the bias correctly will also yeild a big change.

    The bias terminals on the rear of the amp are practiaclly usesless. They measure negative feedback voltage. The problem is that different tubes pull different plate current at the same negative feedback voltage. The easiest method would be to use a bias probe to set the bias on this amp. Also there are many statements that the bias pot is limited and you "cannot" get the bias in the unsafe range. This is totally untrue. I had a quad of sed's that pulled 44ma each with the bias turnned all the way down. So just turning the bias pot blindly for tone could be potentially bad for the tubes.

    The JSX is a great production amp, and can sound great with the bias set right and some good quality tubes.

    All my preamp tubes are NOS V1 Mullard, V2 Sylvania, V3 JAN Philips. V4 JAN GE 12AX7.
     
  3. baron55

    baron55 Member

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    Also you might fing a huge change by getting some good quality tubes. Most tubes that come "stock" with amps are not very good. Amp OEM's put the tubes in that they get from the tube suppliers. They don't check them. For example, my new JSX came stock with EH12AX7's and EH EL34's. On my tube testing equipment, the tubes tested well below spec for new tubes. Not just low by well below. Mutual Tansconductance was low etc.ANd the matching was way off more than 25 %. So just because the amp is new, the new tubes may not be very good. They may be perfectly functional but not sound very good.
     
  4. Greazygeo

    Greazygeo Member

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    I ditched the EL34's in mine for EH 6l6's, try them sometime...to tame the amber channel, get some Sovtek 12ax7WC's...if it has EH12ax7's they are too high gain and saturated for me....

    George
     
  5. DavidE

    DavidE Member

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    I have no problems with the sound of the amp. My only "issue" is that the amber channel has too much gain. I'll see if I have some lower gain preamp tubes sitting around to give them a shot. I'll also check the bias with my Alessandro meter when I take out one of the tube pairs.
     
  6. Baba

    Baba Supporting Member

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    David, sounds like we think alike, I had a XXX head that was the same way, I'm sure they are very similar in design.

    I wanted that classic rock type overdrive, but the middle channel was too over the top, and I couldn't tame it. I don't think a tube swap will help too much, IMO, the channel is just designed that way, I used to set the gain on, say, 2, but it just never cleaned up much.

    Just wanted to let you know I understand where you're coming from, and you're not crazy.
     
  7. baron55

    baron55 Member

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    The JSX has much less sizzle than the XXX. You might try a 12AT7 in the V1 position. The mullard 12AT7's are plentifull and sound great. I am using a high gain mullard 12AX7 in my V1 and no sizzle, just ballsy. The Treble control as the others on the two gain channels are active and very sensitive. Try turning down the treble and compensating with the presence control. You may have already tried this. I am actually running through a Marshall 1960A 4X12 with GT-75's.
     
  8. DavidE

    DavidE Member

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    I was wondering if a lower gain tube in V1 would do the trick. But the more I think about it, I really like the amber channel for what it is. Maybe the best thing to do is just keep a lower gain pedal on the board for use with the clean channel and basically have a 4 channel amp.

    Anyone prefer the lo gain over the hi gain input?
     
  9. DavidE

    DavidE Member

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    How about a 12ay7?
     
  10. chumbucket

    chumbucket Supporting Member

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    I prefer the sound of the high gain channels when I plug into the low input. Unfortunately I like the sound of the clean channel better when I plug in the high input. I'm going to do the pedal thing too but I haven't found one that sounds good into the clean channel. I heard a lot of people say that this amp sounds great with a distortion pedal into the clean channel but the only one I found that cuts it was a Reverend Drivetrain II, and I'm not that knocked out by it.
     
  11. chumbucket

    chumbucket Supporting Member

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    I've also heard that some people were putting a 12DW7 in the V2 and V3 slots to tame the high gain channels a bit. It's a 12AX7/12AU7 hybrid I think?
     
  12. JerryP

    JerryP Member

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    Last I knew the JSX was shipping with EH and Sovtek 12AX7's. The EH can be a bit harsh and bright. I like the Chinese 12AX7's for a smoother more balanced distortion. Try a 12AT7 in the phase inverter spot (the preamp tube right next to the power tubes). Using a 12DW7 or JJ ECC832 in spot #2 (the middle tube in the row of 3 preamp tubes) will help tame it. JJ's overall are a bit warmer and not so harsh.
    Would you guys have a use for reverb on the JSX/XXX amps?
    Jerry
     
  13. DavidE

    DavidE Member

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    I like reverb and miss it a bit on the JSX.
     
  14. baron55

    baron55 Member

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    Peavey has recenty switched to JJ as their tube supplier.
     
  15. DavidE

    DavidE Member

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    I'm going to try the 60 watt mod this week. I confirmed with Roger Crimm that I pull the two outer tubes and set the amp to 4 ohms with an 8 ohm cabinet.
     
  16. Mr_RuLeZ

    Mr_RuLeZ Guest

    If you want to "tame the beast" get the Lower gain re-tube kit for the Peavey Triple XXX at www.eurotubes.com, you dont have to get the power tubes, just the pre-amp tubes and the gain will be more usable and less brutal, if i remember correctly the configuration was:

    V1 - JJ ECC803S
    V2 - JJ ECC832S
    V3 - JJ ECC83S
    V4 (phase inverter) - balanced JJ ECC83S

    That will reduce the gain in the Crunch and Lead channel about a 40%. You will still have all the gain you could ever neeed.
     

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